Ventricular Arrhythmias Flashcards
What is indicative of ventricular ectopy on ECGs?
wide and bizarre QRS
- wide because it takes longer to depolarize
- premature, late
- NOT initiated by P waves
How does ventricular ectopy compare to BBB?
BBBs are preceded by P waves
What primary cardiac diseases and metabolic/endocrine diseases can cause centricular arrhythmias?
CARDIAC = cardiomyopathies, infectious, inflammatory (myositis)
ENDOCRINE = K, Mg, Ca, hyperthyroidism
What drugs and toxins can cause ventricular arrhythmias?
- Digoxin
- Amphetamine
- Theobromine
- Albuterol
What conditions commonly cause ventricular arrhythmia?
- ischemia
- GDV
- sepsis
- splenic disease
- hypoxia
- hypovolemia
- trauma
- pain
- decreased sympathetic innervation - inherited arrhythmias in GSDs
- increased sympathetic innervation - pheochromocytoma
What is the difference between ventricular premature contraction and escape beats?
VPCs = early, randomly placed ventricular beat interrupting normal rhythm
ESCAPE BEAT = late, preceded by a pause where the heart is trying to compensate
What is indicative of a singlet ventricular premature complex (VPC) on ECG?
wide and bizarre QRS complex not initiated by a P wave
- come early and followed by a compensatory pause
What are the most common causes of VPCs in dogs and cats? What treatment is recommended?
- DOGS = large breed cardiomyopathy (Boxers, Dobermans)
- CATS = cardiomyopathy, hyperthyroidism
- congenital disease, CVD, GDV, myocarditis, anesthesia, infiltrative neoplasia, traumatic myocarditis, digitalis toxicity
a few VPCs once in a while can be acceptable in some breeds, but cause should really be investigated and treated (look at ECG > 30s)
What is occurring in this ECG?
VPCs
- wide and bizarre QRS complex not initiated by a P wave
What is occurring in this ECG?
sinus rhythm interrupted by 3 single VPCs
How can the ventricle of origin be differentiated with VPCs on ECG?
RIGHT VENTRICLE = mostly positive QRS
LEFT VENTRICLE = mostly negative QRS
What are some causes of right and left sided disease that can cause VPCs? What most commonly causes disease on both sides?
RIGHT VENTRICLE = arrhythmogenic right ventricular cardiomyopathy (ARVC) in Boxers and Bulldogs, less common (positive QRS)
LEFT VENTRICLE = DCM (Dobermans, Irish Wolfhound, Great Danes), HCM (cats), more common (negative QRS)
EITHER = diffuse myocarditis or myocardial infiltration
VPCs, complexity:
What is occurring in this ECG?
couplet VPCs
What is occurring in this ECG?
one VPC
What is the R on T phenomenon? What 2 things does it indicate?
QRS fires very closely to the preceding T wave
- high risk for development of ventricular fibrillation
- anti-arrhythmic therapy warranted
What is accelerated idioventricular rhythm? How does it appear on ECGs?
runs of VPCs at a rate less than 160 bpm and greated than 40 bpm
- 4 or more VPCs
- looks like VTACH, but much slower
What is occurring in this ECG?
idioventricular rhythm
- 4 VPCs
- HR = 40-160 bpm
What are 5 possible causes of idioventricular rhythm?
- splenectomy
- systemic disease
- myocardial depression
- hypoxia
- myocardial infarction
What is an accelerated idioventricular rhythm (AIVR)? Is treatment necessary?
slow ventricular tachycardia —> alternation between VPCs and normal sinus rhythm
benign arrhythmia - does not perturb hemodynamics, tx not necessary (without ECF, likely nothing was noted wrong with the heart)
What causes the development of accelerated idioventricular rhythm?
non-cardiac disease —> thoracic trauma, GI disease (GDV), splenic disease, pancreatitis, post-splenectomy
What is occurring in this ECG?
accelerated idioventricular rhythm
- VPCs alternate with normal sinus rhythm
What are some clinical signs of single VPCs/AIVR? What therapy is recommended?
- rarely any signs seen
- dropped heart sounds
- irregular/dropped pulses
- weakness, syncope, sudden death
address underlying disease —> pain, stress, hypoxia, hypovolemia, GDV
- specific tx only needed if the patient is hemodynamically affected by the underlying rhythm or it is multifocal
What causes ventricular tachycardia? What 2 things are seen on ECGs?
stimulation of an ectopic ventricular focus
- runs of > VPCs @ >160-180 bpm sustained for > 30s
- QRS complexes with no relationship to P waves (hidden)
When does ventricular tachycardia affect heart function? Why are they especially serious? What conditions are associated?
300 bpm >6-8 bpm
can be pre-fibrillatory and has direct effects on the heart and secondary organs due to poor perfusion
- large dogs with DCM
- uncommon in cats
What is occurring in these ECGs?
sustained ventricular tachycardia
What is the most common cause of sustained ventricular tachycardia? What acute and chronic therapies are recommended?
primary myocardial disease (DCM, ARVC, myocarditis, HCM) —> hemodynamically devastating, potential for rapid decompensation and development of ventricular fibrillation
ACUTE = Lidocaine, Procainamide
CHRONIC = Sotalol, Mexiletine
What is ventricular fibrillation? How do patients present?
non-perfusing rhythm where cells of the myocardium depolarize chaotically
no pulse is felt and cardiac output approaches 0
What are 2 signs of ventricular fibrillation on ECGs?
- rapid, chaotic, irregular rhythm with bizarre waves or oscillations
- no QRS or P waves (large = coarse, small = fine)
What is occurring in this ECG?
ventricular fibrillation
What conditions are associated with ventricular fibrillation?
severe systemic illness or cardiac diseas
- shock, anoxia
- trauma
- myocardial infarction, myocarditis
- electrolyte/acid-base imbalance
- anesthetic reaction
- digoxin toxicity
- cardiac sx
- electrical shock
- hypothermia
What treatment is recommended for ventricular fibrillation?
quick treatment with Epinephrine +/- electrical defibrillation (transthoracic vs. internal) +/- magnesium to stabilize resting membrane potential
- no treatment = likely death
What is ventricular asystole? What is indicative on ECG?
terminal rhythm due to no pacemaker impulse = no contraction, no pulses, no cardiac output with severe sinoatrial block or arrest
no QRS complexes
What is occurring in this ECG?
ventricular asystole
What are 5 parts of treating ventricular asystole?
- start CPR
- epinephrine, atropine
- treat underlying disease
- defibrillation
- precordial thump
rapidly fatal arrhythmia
Ventricular arrhythmias:
